Forest stands were studied to determine if old-growth forest structure could be mimicked in younger stands via overstory manipulation. Cover and species composition of understory plants were systematically sampled in sixteen thinned second-growth stands and sixteen adjacent unthinned second-growth Douglas fir (Pseudotsuga menziesii (Mirabel) Franco.) stands. The stands were thinned twenty-four to thirteen years ago. These were compared to seven nearby old-growth stands. Thinned and unthinned stands had matching elevations, aspect, and soils, yet differed primarily in management treatment. Leaf area indices were determined for these stands. Thinned stands differed from the old-growth and unthinned stands in having significantly higher cover values and species numbers, apparently resulting from increased light to the forest floor and a greater variety of microhabitats created by thinning. Young unthinned and old-growth stands were comparable in terms of cover and richness, but differed in species composition. Diversity indices showed no difference in species diversity between the three types of stands. Ordination of the species/sample data using Detrended Correspondence Analysis showed that understory species composition of the young unthinned and thinned stands was nearly identical. Species composition of old-growth stands differed from thinned and unthinned stands. The ordination indicated that age of the stands, structure of the canopy layers and climate were major determining factors in the species composition of the understory plant communities. Management manipulation of the second growth stands did not yield stands with understory vegetation communities that mimicked those of old-growth stands. The conclusions of this study were: 1) Shrub cover increased with thinning as compared to unthinned and old-growth stands. 2) Thinning increased the species richness of the stands, without increasing the number of exotics. 3) Diversity was not altered by thinning. Old-growth, thinned and unthinned stands did not differ in diversity values. 4) Patterns of community composition in thinned stands were more similar to unthinned equivalent stands than to nearby old-growth. / Graduation date: 1996

Graduation date: 1993

In this thesis, a maximum likelihood receiver to obtain the target range profile that uses the clutter prediction derived from the target-free previous observations is suggested as a fast time processor for pulse compression radar systems. The maximum likelihood receiver is proposed to overcome the range sidelobe problem, which is introduced by the pulse compression method. Conventional methods, such as the matched filter receiver, as fast time processor result in the targets with high radar cross sec- tion masking the low radar cross section targets at the neighboring range cells / since sidelobes of the matched filter is determined by the autocorrelation of the spreading code and linearly proportional to target signal power. An unbiased estimator, like the maximum likelihood receiver in this thesis work does not su&crarr / er from such issues. In addition to that, to suppress the signal dependent interference, namely the clutter, at the output of fast time processor / the previous target-free observations are col- lected and utilized to predict the clutter signal for next time instant. This prediction is used in the maximum likelihood receiver. The clutter prediction is done for the stationary case and the internal clutter motion case, and their SINR performances with the maximum likelihood receiver are evaluated. In conclusion, such an approach managed to have an unbiased estimation of target range profile and the clutter suppression advantage in the fast time.

Thesis (Ph.D.) - University of St Andrews, May 2007.

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Palaeoenvironmental reconstruction of the late Pleistocene and Holocene geological periods for central and southern Africa has been hampered by the erratic distribution of suitable sites, incomplete and inaccurately dated sequences and the limited nature of published data. One geomorphological feature which has supplied valuable evidence for fluctuations in past environmental conditions, is the vlei or dambo. The type-site of these waterlogged features is in south central Africa, but similar features have been described on other continents. The clastic and organic sediments contained within these features are affected by, and therefore reflect to some degree, the environment under which they were formed. The characteristics of the sediments supply information as to their transport and mechanisms of deposition. From these processes, the environmental conditions at the time of vlei formation can be inferred. The environmental history of the Eastern Cape region has been considerably neglected, and is far less well understood than other countries such as Malawi, Zambia and Zimbabwe. A study site in the Winterberg Range (Eastern Cape) was selected which permitted the comparison of two vleis, the objective being to establish an accurate late Pleistocene sediment chronology for the entire plateau area. Radiocarbon dates from organic layers indicate that these sediments span the last 12 000 years BP, suggesting that organic accumulation at this site began at roughly the same time as at sites further afield. The vlei sediments are analysed in terms of their morphology, particle slze distribution, and other physical and chemical characteristics. These data facilitate the construction of detailed stratigraphic diagrams and a chronological summary of sediment accumulation, from which the period and governing processes of vlei development under changing environments may be described. It is found that the Winterberg vleis contain sediments which respond to changes in the prevailing environment. This makes these sediments useful indices from which to trace such changes during the late Pleistocene and Holocene times. These features are found to be similar in many respects to those described elsewhere in Southern Africa. The study attempts to provide greater understanding of contemporary vlei processes and emphasises the necessity of their preservation, as finite and valuable resources, by future generations

Advancement of micro-electro-mechanics and wireless communication have proliferated the deployment of large-scale wireless sensor networks. Due to cost, size and power constraints, at most a few sensor nodes can be equipped with a global positioning system; such nodes (whose positions can be accurately determined) are referred to as anchors. However, one can deter-mine the distance between two nearby sensors using some form of local communication. The problem of computing the positions of the non-anchor nodes from the inter-sensor distances and anchor positions is referred as sensor network localization (SNL). In this dissertation, our aim is to develop an accurate, efficient, and scalable localization algorithm, which can operate both in the presence and absence of anchors. It has been demon-strated in the literature that divide-and-conquer approaches can be used to localize large net-works without compromising the localization accuracy. The core idea with such approaches is to partition the network into overlapping subnetworks, localize each subnetwork using the available distances (and anchor positions), and finally register the subnetworks in a single coordinate system. In this regard, the contributions of this dissertation are as follows: We study the global registration problem and formulate a necessary “rigidity” condition for uniquely recovering the global sensor locations. In particular, we present a method for efficiently testing rigidity, and a heuristic for augmenting the partitioned network to enforce rigidity. We present a mechanism for partitioning the network into smaller subnetworks using cliques. Each clique is efficiently localized using multidimensional scaling. Finally, we use a recently proposed semidefinite program (SDP) to register the localized subnetworks. We develop a scalable ADMM solver for the SDP in question. We present simulation results on random and structured networks to demonstrate the pro-posed methods perform better than state-of-the-art methods in terms of run-time, accuracy, and scalability.

This work describes a method based on three stages for reconstructing a model from a given set of scanned meshes obtained from 3D scanners. Meshes scanned from different scanner s view points have their representation in local coordinate systems. Therefore, for final model reconstruction, an alignment of the meshes is required. The most popular algorithm for cloud data registration is the ICP algorithm. However, ICP requires an initial estimate of mesh alignment, which is, many times, done manually. To automate this process, this work uses a surface representation called spin-images to identify overlap areas between the meshes and to estimate their alignment. After this initial registration, the alignment is refined by the ICP algorithm, and finally the model is reconstructed using a method called VRIP. / Fundação de Amparo a Pesquisa do Estado de Alagoas / Este trabalho descreve um método baseado em três etapas para reconstrução de modelos a partir de malhas capturadas de scanners 3D. Malhas obtidas a partir de diferentes pontos de visão de um scanner têm sua representação em sistemas de coordenadas local. Portanto, para a reconstrução final do modelo, é necessário realizar um alinhamento dessas malhas, ou registro. O algoritmo mais famoso para realizar registro de nuvens de pontos é o algoritmo ICP. Porém, um dos requisitos desse algoritmo é uma estimativa inicial do alinhamento das malhas, que muitas vezes é feita manualmente. Para automatizar esse processo, este trabalho utiliza descritores spin-image para identificar regiões de sobreposição entre as malhas e estimar seus alinhamentos. Após este registro inicial, o alinhamento é refinado através do algoritmo ICP, e finalmente o modelo é reconstruído usando uma técnica chamada VRIP.

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Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Uso do espaço é um padrão bem estudado em ecologia. Entretanto, formação de área de vida e posição relativa dos abrigos com área de uso são pouco estudados, principalmente para marsupiais didelfídeos. Dentre estes animais, podemos destacar Caluromys philander, devido ao seu baixo registro em armadilhas na Mata Atlântica e características peculiares dentro do grupo, como seu desenvolvimento, longevidade e hábito alimentar. Neste estudo foram investigadas as formações das áreas de uso destes animais através da comparação com seus movimentos diários, e a posição dos seus abrigos dentro das suas áreas de uso. Para isso foram monitorados seis indivíduos de C. philander através de colares rádio transmissores. Estes indivíduos se deslocaram em média 534 153 m por noite. Além disso, apresentaram área diária de 9548 3591 m e área de vida de 2,8 0,4 ha. Noventa e sete por cento das áreas diárias apresentaram sobreposição entre si, com média de 19,4% de sobreposição. Não houve diferença nos locais dos abrigos dos indivíduos monitorados, dentro dos seus Mínimos Polígonos Convexos. Entretanto, estes mesmos abrigos não estiveram localizados nas áreas de maior intensidade de uso. A média de abrigos utilizados por indivíduo foi de 6,3 (3-10) com utilização média de 2,9 (1-17) vezes em cada abrigo, sendo que 48% das vezes os animais só possuíram um registro em cada abrigo, demonstrando baixa fidelidade. Entretanto, dois indivíduos apresentaram diferença de utilização entre seus abrigos, com três destes sendo mais utilizados que os outros. O trabalho sugere que os indivíduos de C. philander monitorados apresentam área de vida propriamente dita (restrita), onde ocorrem as sobreposições entre suas áreas diárias. C. philander utilizam mais de um abrigo em suas vidas, trocando com frequência de abrigos, apesar de alguns destes abrigos poderem ser mais utilizados que outros. Além disso, os abrigos destes animais não são localizados nas suas áreas de maior intensidade de uso. / Use of space is a well studied topic in ecology. However, the structuring of the home range and shelters position, have not received enough attention, especially for didelphid marsupials. One of these, Caluromys philander, is an interesting species because of its low record in traps studies in the Atlantic Forest and its unique characteristics among marsupials related to development, longevity and feeding habits. The present study analyses how daily movements can contribute to the home range formation and how the shelters are positioned within the home range of these animals. Six individuals of C. philander were equipped with radio transmitters necklaces and followed during the night. These individuals moved 534 153 m in average per night. They also had daily ranges of 9548 3591 m and home ranges of 2.8 0.4 ha. There was a 97% overlap between days, with an average of 19.4%. There was no difference in shelters positions and Minimum Convex Polygon areas, although these same shelters were not located in the areas with the greatest use intensity. The average number of shelters used per individual was 6.3 (3-10), with an average of 2.9 (1-17) records per shelter, where shelters were used only one time in 47% of the cases, suggesting low shelter fidelity of these animals. However, two individuals showed difference of shelters use, with three of those being used more than the others. Therefore, I conclude that these individuals of C. philander have real home ranges, where they concentrate their daily movements. C. philander uses more than one shelter in its life, changing shelters frequently, although some shelters can be more used than others. Forthermore, shelters were not located in the areas with the greatest use intensity.